Grinding is a precision finishing process for improving the surface finish, size, and shape of the part with very tight tolerances. Often required in medical and food processing to reduce the possibility of areas for microbes or bacteria to grow, it completes parts in fluid applications such as nozzles, injectors, or fittings, ensuring the smooth flow of the liquid or gas.

A typical range of Average Surface Roughness (Ra) of 8-16 µ (micron) inches can be achieved through a grinding process. You would need a microscope to see the surface difference in this roughness range; however, this finish would feel very smooth to the touch. Dimensional grinding provides control of dimensions of +/- 0.0001 inches and the part’s concentricity, runout, or cylindricity within 0.0002 inches. This is finer than the diameter of human hair. These tight tolerances are typically specified for the precision assembly of parts or precision control of flow through a nozzle.

MacFab’s finishing capability includes two different methods:

  • Surface grinding for precision flat plates
  • Inner Diameter (ID) honing of a hole completed in Sunnen honing machines

Surface Grinding


Imagine placing two iPad Minis together, short edge to short edge. Your part will fit into an envelope of this size for grinding in our machines. Applications utilizing surface grinding, like testing platforms, qualifying surfaces for precision machining, or plate mounting in an assembly, require tight tolerance dimensions or geometrically flat and parallel elements.

Inner Diameter Honing


Our machine can hone a hole the diameter of the lead in a pencil up to the inside of a coffee can and just over a foot long. Honing must be a slow grinding process to prevent significant heat from transferring to the workpiece and to maintain the piece’s geometric shape and dimensions.

Materials Commonly Honed

  • Alloy steel, such as 4140
  • Heat-treated steels
  • Stainless steel, such as PH 17-4
  • Heat-treated stainless steel

While other manufacturers may outsource grinding to a third party, our vertical integration allows us to provide improved cost, quality, and lead times on parts requiring a grinding operation.